Generally, when making ice by underwater supercooling release, if a so-called residual supercooled state exists in which ice is mingled in supercooled water and the residual supercooled state is transferred downstream while kept in the supercooled state, ice adheres to the wall of the flow channel extending downstream from a supercooling releasing section to an ice thermal storage tank, and it may happen that the flow channel is clogged due to the growth of the adhered ice.
That is, the growth of the ice adhered to the wall of the flow channel is fostered by the contact with the ambient supercooled water.
As the adhesion of the ice crystal grown on the wall where the flow velocity is small is strong and the adhered ice is difficult to be separated, ice adheres all over the wall and the flow channel becomes narrowed if such a state continues for a long period.
Further, significantly high pressure is needed to separate the ice grown on the wall, and in addition, sherbet-like ice becomes consolidated due to the force of flow resistance, and finally the pipe conduit(flow channel) may be completely clogged. Therefore, when making ice by underwater supercooling release, it is necessary to prevent the clogging in the downstream pipe conduit by releasing residual supercooled state.
A method of releasing residual supercooled state is disclosed, for example, in Japanese Patent Application Publication No. 5-149653 (hereafter referred to as the example of prior art).
In the example of prior art, as shown in FIG. 1, a completing section of supercooling release is provided downstream after supercooling is released. For example, in FIG. 1(a), a throttling section 110 is provided downstream of a underwater supercooling releasing section 108, further an enlargement section 109a and a tapered section 109b for throttling the flow area to that of the throttling section 110 are provided downstream of the throttling section 110. The throttling section 110, enlargement section 109a, and tapered section 109b compose the completion section of supercooling release.
In the completion section of supercooling release shown in FIG. 1(a), complete release of supercooling is enhanced by the agitation generated as a result of abrupt enlargement of water flow section area after the water passes through the supercooling releasing section.
In the completion section of supercooling release shown in FIG. 1(b), a plurality of enlargement section 109a1 and 109a2 are provided after the throttling section 110. In the completion section of supercooling release shown in FIG. 1(c), an impingement member 109c is located in the center of the enlargement section 109a for generating a turbulent flow.
As described above, in the example of prior art, a turbulent flow is generated in the downstream flow channel to release the residual supercooled state by the agitation induced by the turbulence.
However, it is necessary, in the example of prior art, to provide at least a throttling section, enlargement section, and tapered section. As a result, a problem is encountered that not only the downstream piping must inevitably be long but the ice making apparatus becomes large and complicated.
Further, in the example of prior art, the residual supercooled state is released only by the agitation induced by flow turbulence, so that the residual supercooled state can not be released enough and as a result clogging may occur in the pipe conduit.